What types of adaptations would be needed by organisms that live in a river?

Organisms living in a river typically require adaptations to deal with the flowing water and varying environmental conditions. These adaptations may include streamlined bodies to reduce resistance against currents, specialized gills or breathing mechanisms for extracting oxygen from water, and the ability to cling to surfaces to avoid being swept away. Additionally, some species may develop reproductive strategies that align with seasonal changes in water levels and flow.